From 999dde7339787a0efac5b874b6ccf14b7dace8e8 Mon Sep 17 00:00:00 2001
From: Jishnu Bhattacharya <jishnub.github@gmail.com>
Date: Wed, 8 May 2024 09:40:46 +0530
Subject: [PATCH] Unicode: assume foldable ccall in category_code (#54394)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Following on from https://github.com/JuliaLang/julia/pull/54346, this
marks the `ccall` in `category_code` as foldable. This lets us compute
the results of several functions at compile time, such as:
```julia
julia> @code_typed (() -> isletter('C'))()
CodeInfo(
1 ─     return true
) => Bool

julia> @code_typed (() -> isnumeric('C'))()
CodeInfo(
1 ─     return false
) => Bool

julia> @code_typed (() -> ispunct('C'))()
CodeInfo(
1 ─     return false
) => Bool
```
---
 base/strings/unicode.jl |  2 +-
 test/char.jl            | 12 +++++++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/base/strings/unicode.jl b/base/strings/unicode.jl
index b659ec080680b..9a44912946205 100644
--- a/base/strings/unicode.jl
+++ b/base/strings/unicode.jl
@@ -350,7 +350,7 @@ function category_code(c::AbstractChar)
 end
 
 function category_code(x::Integer)
-    x ≤ 0x10ffff ? ccall(:utf8proc_category, Cint, (UInt32,), x) : Cint(30)
+    x ≤ 0x10ffff ? (@assume_effects :foldable @ccall utf8proc_category(UInt32(x)::UInt32)::Cint) : Cint(30)
 end
 
 # more human-readable representations of the category code
diff --git a/test/char.jl b/test/char.jl
index 5a522dfd1c743..5da92121b1630 100644
--- a/test/char.jl
+++ b/test/char.jl
@@ -361,12 +361,17 @@ end
     @test convert(ASCIIChar, 1) == Char(1)
 end
 
-@testset "foldable isuppercase/islowercase" begin
+@testset "foldable functions" begin
     v = @inferred (() -> Val(isuppercase('C')))()
     @test v isa Val{true}
     v = @inferred (() -> Val(islowercase('C')))()
     @test v isa Val{false}
 
+    v = @inferred (() -> Val(isletter('C')))()
+    @test v isa Val{true}
+    v = @inferred (() -> Val(isnumeric('C')))()
+    @test v isa Val{false}
+
     struct MyChar <: AbstractChar
         x :: Char
     end
@@ -377,4 +382,9 @@ end
     @test v isa Val{true}
     v = @inferred (() -> Val(islowercase(MyChar('C'))))()
     @test v isa Val{false}
+
+    v = @inferred (() -> Val(isletter(MyChar('C'))))()
+    @test v isa Val{true}
+    v = @inferred (() -> Val(isnumeric(MyChar('C'))))()
+    @test v isa Val{false}
 end